1. Field of the Invention
The present invention relates to a view finder display device having a liquid crystal cell for displaying the photographic informations and various kinds of alarms.
2. Description of the Prior Art
In case of the conventional device for displaying the photographic informations such as the measured value of the brightness of the object to be photographed or the alarm for the fact that the photographic informations are out of the mechanically linked range for obtaining the proper exposure, an ampere meter is supplied with a current corresponding to the measured light value or the preset exposure value in such a manner that the measured light value is displayed at the display part by the position of the pointer of the ampere meter. However there are so many inconveniences, for example the device is subject to breakage, being provided with movable means such as ampere meter, the invasion of dust into the focus plate part through the opening for the movable means hinders the view field, it is difficult to build the device itself in a camera with small space, much noise takes place along the boundary between the display part and the object view field or other photographic informations than that of the object to be photographed are always seen in the object view field. Further, there are such devices in which the pointer of the ampere meter is brought out of the display window or brought into the alarm zone provided at the upper or the lower end of the display part, whereby either it is difficult for the photographer to find the pointer or the red alarm zone is always seen in the view field, which is troublesome for the photographer. Further, in case of such type of the device in which the mechanically linked alarm display plate projects into the display part only at the time of alarm, it is mechanically so complicated that the manufacturing cost is high and there is much possibility for damage. Further in case of the type of device in which LED (illuminating diode) illuminates the power consumption is large, which is also inconvenient.
In case of the conventional device by means of which the battery can be checked, the display LED (illuminating diode) is connected to the power source through a switching circuit in such a manner that the consumption of the battery is checked, observing whether the LED illuminates or not. However, LED consumes much power, the battery checking itself consumes the battery, which is also inconvenient.
Further in case of the type of the device in which the pointer of the ampere meter for displaying the measured light value in the view finder serves further to display the battery checking, it is difficult to tell the battery checking display from the light measurement display, while the display of the consumption of the battery does not sufficiently serve as an alarm.
Further in case some informations are displayed in the view finder whereby the display part is in the photographic view field frame, the decision of the composition of the picture is hindered, which is troublesome, while in case the display part is out of the photographic view field frame the display becomes obscure and there is a danger that the photographer should fail to observe the alarm display such as for the improper exposure.
Thus in order that one display can be observed along to different directions at the same time it is necessary to prepare each one display device or a complicated optical system, for example in order that the information display output can be observed both outside of the camera and in the view finder it is necessary to provide the display devices at two positions, which is not profitable.
So far various kinds of display devices having a liquid crystal, for example, the seven-element display by means of a digital driving circuit, the analog display by means of a high voltage, the integral analog display by means of the digital driving circuit and so on.
Recently for those display devices, the liquid crystal of field effective type has come to be used, whereby the liquid crystal cell of this type consists of polarization plates so that the light is attenuated by the polarization plates in such a manner that the sufficient brightness can not be obtained for the brightness, whereby when it is used as the photographic information display device in the view finder the discrimination of the display is difficult even at the place with the brightness in the ordinary room.